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The 2021 ICD-O-3.2 Update includes papillary microcarcinoma (8341/3) as the preferred term for thyroid primaries (C739). However, there are multiple SINQ entries instructing registrars not to use code 8341/3 for diagnoses of micropapillary carcinoma of the thyroid (including SINQ 20071076, 20081127, 20110027, 20150023, and 20180008).

SINQ 20150023 specifically indicates: Per the WHO Tumors of Endocrine Organs, for thyroid primaries/cancer only, the term micropapillary does not refer to a specific histologic type. It means that the papillary portion of the tumor is minimal or occult (1 cm or less in diameter) and was found incidentally. WHO does not recognize the code 8341 and classifies papillary microcarcinoma of the thyroid as a variant of papillary thyroid carcinoma and codes histology to 8260. If the primary is thyroid and the pathology states papillary microcarcinoma or micropapillary carcinoma, code 8260 is correct.

Does this clarification apply to cases diagnosed 2021 and later? If WHO feels the term micropapillary still does not refer to a specific histologic type for the thyroid, why is 8341/3 listed as a preferred term for this morphology/site combination? For cases 2021 and later, should a diagnosis of Incidental papillary thyroid microcarcinoma (3 mm) in left lower pole, be coded as 8341/3 per the ICD-O-3.2, or as 8260/3 per clarification in multiple SINQ entries?

This question was prompted from preparing SEER*Educate coding exercises. We will use the answer as a reference in the rationales.

Example: An MRI Spine showed a large expansile mass arising from the sella turcica and extending into the suprasellar cistern, but the radiologist only noted: The leading differential considerations include pituitary macroadenoma or a large suprasellar base meningioma. The patient was subsequently pathologically diagnosed with a pituitary adenoma. It is unclear if the diagnosis date should be coded to the MRI date.

There are two existing SINQ questions regarding the term consider. SINQ 20061094 confirms a diagnosis that is considered to be is reportable because it is unambiguous, but SINQ 20081033 states the phrase malignancy is highly considered is not a reportable ambiguous term.

How should we interpret differential considerations? If differential considerations is equivalent to a differential diagnosis, then this patient was clinically diagnosed on imaging. However, if differential considerations is not reportable, then there was no diagnosis prior to the resection.

Is this histologic terminology synonymous with 8071/2 Differentiated-type vulvar intraepithelial neoplasia?

Per the 7/20/2018 updates to the 2018 ICD-O-3 Histology list, the reportability flag was changed from N to Y for Differentiated-type vulvar intraepithelial neoplasia as well as Differentiated penile intraepithelial neoplasia, both 8071/2. It appears that both SINQ 20180020 and the second half of SINQ 20160069 are no longer valid and should be deleted.

SINQ 20200022 indicates that cases originally diagnosed as in situ do not have a new primary when a new invasive tumor with a different histology is diagnosed within 5 years. Should histology and/or behavior get updated for the in situ breast primary?

The ICD-O-3.2 Coding Table includes hybrid oncocytic chromophobe tumor as a related term for histology code 8317 (Renal cell carcinoma, chromophobe type). However, this related term is not discussed in the implementation guidelines as being a new term/reportable tumor. The Solid Tumor Rules do not indicate a hybrid oncocytic chromophobe tumor is reportable; however, if a registrar only looked at the ICD-O-3.2 Coding Table, it may seem as though this histology should be collected.

The term hybrid oncocytic chromophobe tumor was not included in the Solid Tumor Rules as a subtype/variant of RCC, or as an equivalent term for chromophobe RCC. There is a SINQ (20180047) that states not to report renal hybrid oncocytic tumor, despite the fact these tumors exhibit mixed features of both oncocytoma and chromophobe RCC. For cases diagnosed 2021 and later, should the clarification in the SINQ apply? Or should the ICD-O-3.2 Coding Table be used which indicates this is a reportable diagnosis? If the standard setters decided not to implement use of hybrid oncocytic chromophobe tumor for 2021, can clarification be added to the Solid Tumor Rules or Implementation Guidelines?

This question was prompted from preparing SEER*Educate coding exercises. We will use the answer as a reference in the rationales.

Patient had a radical pharyngectomy showing a glossotonsillar sulcus tumor with high grade squamous cell carcinoma and adjacent high grade mucoepidermoid carcinoma. The pathologist commented, the tumor is composed of high grade mucoepidermoid carcinoma and high grade conventional-type squamous cell carcinoma that are immediately adjacent to one another. Given that the tumors are arising so close together and could represent a single neoplastic process with divergent morphologies, they are staged together.

Employing Solid Tumor Manual Rule M1 (single primary if unable to determine if there is a single or multiple tumors), it was determined that this should be reported as a single tumor because the pathologist referred to the case as both a tumor singular and tumors pleural. However, the Solid Tumor Manual Histology Rules for a Single Tumor do not appear to have an instruction for coding this histology combination.

Example: Posterior fossa tumor resection final diagnosis was medulloblastoma, WHO Grade IV. The diagnosis comment notes the current tumor resection reveals large irregular reticulin-free nodules with streams of neoplastic cells in a fibrillary background in association with narrow reticulin-rich internodular strands of poorly differentiated neoplastic cells. Taken together, these findings are indicative of medulloblastoma with extensive nodularity. The diagnosis comment provided only one histology.

Per the 2018 Solid Tumor Manual, Malignant CNS, Priority Order for Using Documentation to Identify Histology instructions, an addendum or comment has priority over the final diagnosis. Although indicative is not listed on any ambiguous terminology list, is this an ambiguous diagnosis that must be ignored? Or does the diagnosis comment in this case provide a single, specific diagnosis of medulloblastoma with extensive nodularity?

Rule H13 states to code the histology to metaplastic carcinoma when there is metaplastic carcinoma (or a subtype/variant) and invasive carcinoma NST. This rule makes no mention of lobular carcinoma. However, in Table 3, Note 2 for metaplastic carcinoma (8575) states metaplastic carcinoma, NOS and subtypes are almost always mixed with invasive mammary carcinoma, NST and at times lobular carcinoma. These tumors should be coded to metaplastic regardless of percent invasive mammary carcinoma or lobular carcinoma present.

While Table 2 (the mixed histology code table) does include an entry for metaplastic carcinoma AND carcinoma NST OR lobular carcinoma, it is unclear why lobular carcinoma has not been added to Rule H13 as well.

If a single tumor has metaplastic plus lobular carcinoma, Rule H13 does not apply and one has to continue through the rules. Unfortunately, the next rule registrars would be tempted to use is Rule H18: Code the histology that comprises greater than 50% of tumor when two histologies are on different rows in Table 3. This Rule does not state it does NOT apply to metaplastic carcinoma (only mucinous). So, if for some reason the lobular was greater than 50%, the incorrect histology would be coded (unless the registrar happened to remember Note 2 in the metaplastic carcinoma entry in Table 3).

This question was prompted from preparing SEER*Educate coding exercises. We will use the answer as a reference in the rationales.